681 research outputs found

    SPIRAL Phase A: A Prototype Integral Field Spectrograph for the AAT

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    We present details of a prototype fiber feed for use on the Anglo-Australian Telescope (AAT) that uses a dedicated fiber-fed medium/high resolution (R > 10000) visible-band spectrograph to give integral field spectroscopy (IFS) of an extended object. A focal reducer couples light from the telescope to the close-packed lenslet array and fiber feed, allowing the spectrograph be used on other telescopes with the change of a single lens. By considering the properties of the fibers in the design of the spectrograph, an efficient design can be realised, and we present the first scientific results of a prototype spectrograph using a fiber feed with 37 spatial elements, namely the detection of Lithium confirming a brown dwarf candidate and IFS of the supernova remnant SN1987A.Comment: 41 pages, 15 figures, 3 tables; accepted by PAS

    The Impact of CEO Turnover on Equity Volatility

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    A change in executive leadership is a significant event in the life of a firm. Our paper investigates a potentially significant consequence of a CEO turnover: a change in equity volatility. We develop several hypotheses about how CEO changes might affect stock price volatility, and test these hypotheses using a sample of 872 CEO changes over the 1979-1995 period. We find that volatility increases following a CEO turnover, even for the most frequent type, when a CEO leaves voluntarily and is replaced by someone from inside the firm. Our results indicate that forced turnovers, which are expected to result in large strategy changes, increase volatility more than voluntary turnovers. Outside successions, which are expected to result in a successor CEO with less certain skill in managing the firm's operations, increase volatility more than inside turnovers. We also document a greater stock-price response to earnings announcements around CEO turnover, consistent with more informative signals of value driving the increased volatility. Controls for firm-specific characteristics indicate that the volatility changes cannot be entirely attributed to factors such as changes in firm operations, firm size, and both volatility change and performance prior to the turnover

    Comparison of cause of death between ANZDATA and the Australian national death index.

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    Aim: The aim of the present study was to understand the differences in how cause of death for patients receiving renal replacement therapy in Australia is recorded in The Australian and New Zealand Dialysis and Transplant Registry (ANZDATA) compared to the National Death Index (NDI). Methods: Data linkage was performed between ANZDATA and NDI for all deaths in the period 1980-2013. Cause of death was classified according to ICD-10 chapter. Overall and chapter specific agreement were assessed using the Kappa statistic. Descriptive analysis was used to explore differences where there was disagreement on primary cause of death. Results: The analysis cohort included 28 675 patients. Ninety five percent of ANZDATA reported deaths fell within +/- 3 days of the date recorded by NDI. Circulatory death was the most common cause of death in both databases (ANZDATA 48%, NDI 32%). Overall agreement at ICD chapter level of primary cause was poor (36%, kappa 0.22). Agreement was best for malignancy (kappa 0.71). When there was disagreement on primary cause of death these were most commonly coded as genitourinary (35%) and endocrine (25.0%) in NDI, and circulatory (39%) and withdrawal (24%) in ANZDATA. Sixty-nine percent of patients had a renal related cause documented as either primary or a contributing cause of death in the NDI. Conclusion: There is poor agreement in primary cause of death between ANZDATA and NDI which is in part explained by the absence of diabetes and renal failure as causes of death in ANZDATA and the absence of 'withdrawal' in NDI. These differences should be appreciated when interpreting epidemiological data on cause of death in the Australian end stage kidney disease population

    The Influence Of Neutron Capture Rates On The Rare Earth Region Of The r-Process Abundance Pattern

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    We study the sensitivity of the r-process abundance pattern to neutron capture rates along the rare earth region (A~150 to A~180). We introduce the concepts of large nuclear flow and flow saturation which determine the neutron capture rates that are influential in setting the rare earth abundances. We illustrate the value of the two concepts by considering high entropy conditions favorable for rare earth peak production and identifying important neutron capture rates among the rare earth isotopes. We also show how these rates influence nuclear flow and specific sections of the abundance pattern.Comment: 14 pages, 7 figures, submitted to PR

    Empirical evidence of study design biases in randomized trials:Systematic review of meta-epidemiological studies

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    To synthesise evidence on the average bias and heterogeneity associated with reported methodological features of randomized trials.Systematic review of meta-epidemiological studies.We retrieved eligible studies included in a recent AHRQ-EPC review on this topic (latest search September 2012), and searched Ovid MEDLINE and Ovid EMBASE for studies indexed from Jan 2012-May 2015. Data were extracted by one author and verified by another. We combined estimates of average bias (e.g. ratio of odds ratios (ROR) or difference in standardised mean differences (dSMD)) in meta-analyses using the random-effects model. Analyses were stratified by type of outcome ("mortality" versus "other objective" versus "subjective"). Direction of effect was standardised so that ROR < 1 and dSMD < 0 denotes a larger intervention effect estimate in trials with an inadequate or unclear (versus adequate) characteristic.We included 24 studies. The available evidence suggests that intervention effect estimates may be exaggerated in trials with inadequate/unclear (versus adequate) sequence generation (ROR 0.93, 95% CI 0.86 to 0.99; 7 studies) and allocation concealment (ROR 0.90, 95% CI 0.84 to 0.97; 7 studies). For these characteristics, the average bias appeared to be larger in trials of subjective outcomes compared with other objective outcomes. Also, intervention effects for subjective outcomes appear to be exaggerated in trials with lack of/unclear blinding of participants (versus blinding) (dSMD -0.37, 95% CI -0.77 to 0.04; 2 studies), lack of/unclear blinding of outcome assessors (ROR 0.64, 95% CI 0.43 to 0.96; 1 study) and lack of/unclear double blinding (ROR 0.77, 95% CI 0.61 to 0.93; 1 study). The influence of other characteristics (e.g. unblinded trial personnel, attrition) is unclear.Certain characteristics of randomized trials may exaggerate intervention effect estimates. The average bias appears to be greatest in trials of subjective outcomes. More research on several characteristics, particularly attrition and selective reporting, is needed

    Concomitant invasive pneumococcal disease in a patient with COVID-19 – A case report from the Louisville Epidemiology Study

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    A 60-year-old male presented to the Emergency Department (ED) with a one-two day history of confusion, headache, and subjective fever. Because he had met with a contact two days prior to admission who had recently traveled from the Bahamas, a COVID-19 nasopharyngeal (NP) and oropharyngeal (OP) polymerase chain reaction (PCR) test was ordered. He was diagnosed with bacterial meningitis based on presenting neurologic symptoms and the identification of Streptococcus pneumoniae from blood cultures. The COVID-19 NP and OP test returned positive, although he never developed shortness of breath, cough, other respiratory symptoms, diarrhea, abdominal pain, nausea, vomiting, or any change in sense of smell or taste. On day three of admission, the patient had improved clinically on intravenous (IV) antibiotics and was discharged home with instructions to self-quarantine. This case demonstrates the possibility of co-infections with COVID-19 and raises the possibility of an association between COVID-19 and patient susceptibility to invasive pneumococcal disease (IPD)

    False-negative SARS-CoV-2 Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) is an Important Consideration for Patient Management and Infection Prevention: A Case Report from The Louisville COVID-19 Epidemiology Study

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    We report a case of false negative SARS-CoV-2 RT-PCR on nasopharyngeal swab. Treating clinicians and infection preventionists should maintain a high suspicion for COVID-19 in the appropriate clinical setting despite negative test results. Utilization of chest CT should be strongly considered in the diagnostic work-up for suspected COVID-19, particularly in areas with limited RT-PCR availability
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